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H D, A A M, M G, S M, C K. Study of Photoneutron Production for the 18 MV Photon Beam of the Siemens Medical linac by Monte Carlo Simulation. J Biomed Phys Eng 2020; 10:679-690. [PMID: 33364205 PMCID: PMC7753258 DOI: 10.31661/jbpe.v0i0.939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2018] [Accepted: 06/05/2018] [Indexed: 11/22/2022]
Abstract
Background: Considering the importance of photoneutron production in linear accelerators, it is necessary to describe and measure the photoneutrons produced around modern linear accelerators. Objective: The aim of the present research is to study photoneutron production for the 18 MV photon beam of a Siemens Primus Plus medical linear accelerator. Material and Methods: This study is an experimental study. The main components of the head of Siemens Primus Plus linac were simulated using MCNPX 2.7.0 code. The contribution of different components of the linac in photoneutron production, neutron source strength, neutron source strength and photon and electron spectra were calculated for the flattening filter and flattening filter free cases for the 18 MV photon beam, and was scored for three fields of 5 × 5 cm2, 10 × 10 cm2 and 20 × 20 cm2 in size. Results: The results show that the primary collimator has the largest contribution to production of neutrons. Moreover, the photon fluence for the flattening filter free case is 8.62, 6.51 and 4.62 times higher than the flattening filter case for the three fields, respectively. The electron fluences for the flattening filter free case are 4.62, 2.93 and 2.79 times higher than with flattening filter case for the three fields under study, respectively. In addition to these cases, by increasing the field size, the contribution of neutron production related to the jaws is reduced, so that when the field size increases from 5 × 5 cm2 to 20 × 20 cm2, a 17.93% decrease in photoneutron production was observed. Conclusion: In all of the accelerators, the neutron strength also increases with increasing energy. The calculated neutron strength was equal to 0.83×1012 neutron Gy −1 at the isocenter.
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Affiliation(s)
- Dowlatabadi H
- PhD, Physics Department, School of Sciences, Payame Noor University of Mashhad, Mashhad, Iran
| | - Mowlavi A A
- PhD, Physics Department, School of Sciences, Hakim Sabzevari University, Sabzevar, Iran
- PhD, International Centre for Theoretical Physics, Associate Federation Scheme, Medical Physics Field, Trieste, Italy
| | - Ghorbani M
- PhD, Biomedical Engineering and Medical Physics Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammadi S
- PhD, Physics Department, School of Sciences, Payame Noor University of Mashhad, Mashhad, Iran
| | - Knaup C
- PhD, Comprehensive Cancer Centers of Nevada, Las Vegas, Nevada, USA
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Vysakh R, Musthafa MM, Midhun CV, Niyas P, Anjana PT, Krishnan MPA, Ranjith CP, Irfad MP, Ganapathi Raman R. Experimental determination of thermal neutron fluence around Elekta Versa HD linear accelerator for various photon energies. Biomed Phys Eng Express 2020; 6:055018. [PMID: 33444249 DOI: 10.1088/2057-1976/abac90] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A complex neutron spectrum generated along with a useful photon beam imposes an additional radiation protection risk around medical linear accelerators (linac). The thermal neutron component of this complex neutron spectrum formed during different photon modes of operation of Elekta Versa HD linac has been quantified using Indium foil activation technique. The thermal neutron fluence (Φ th ) at isocenter for 15 MV, 10 MV and 10 MV FFF beams was found to be 2.45 × 105, 4.35 × 104 and 3.2 × 104 neutrons cm-2 Gy-1, respectively. The analysis shows a reduction in the Φ th as the flattening filter is being taken out from the beam path. A negative correlation in Φ th with respect to field size has been observed with an average 18% reduction in Φ th per monitor units as field size changes from 10 cm × 10 cm to 40 cm × 40 cm. For particular field size and photon energy, Φ th was found to be uniform across the patient plane. From the measured gamma ray spectrum inside the treatment room six major isotopes have been identified which were 122Sb, 187W, 82Br, 56Mn, 24Na and 28Al.
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Affiliation(s)
- R Vysakh
- Department of Physics, Noorul Islam Centre for Higher Education, Kumaracoil- 629 180, Kanyakumari District, Tamil Nadu, India. Department of Medical Physics and Radiation Safety, MVR Cancer Centre & Research Institute, Calicut, India
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3
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Evaluation of in-field neutron production for medical LINACs with and without flattening filter for various beam parameters - Experiment and Monte Carlo simulation. RADIAT MEAS 2018. [DOI: 10.1016/j.radmeas.2018.04.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Elazhar H, Deschler T, Létang JM, Nourreddine A, Arbor N. Neutron track length estimator for GATE Monte Carlo dose calculation in radiotherapy. Phys Med Biol 2018; 63:125018. [PMID: 29790859 DOI: 10.1088/1361-6560/aac768] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The out-of-field dose in radiation therapy is a growing concern in regards to the late side-effects and secondary cancer induction. In high-energy x-ray therapy, the secondary neutrons generated through photonuclear reactions in the accelerator are part of this secondary dose. The neutron dose is currently not estimated by the treatment planning system while it appears to be preponderant for distances greater than 50 cm from the isocenter. Monte Carlo simulation has become the gold standard for accurately calculating the neutron dose under specific treatment conditions but the method is also known for having a slow statistical convergence, which makes it difficult to be used on a clinical basis. The neutron track length estimator, a neutron variance reduction technique inspired by the track length estimator method has thus been developped for the first time in the Monte Carlo code GATE to allow a fast computation of the neutron dose in radiotherapy. The details of its implementation, as well as the comparison of its performances against the analog MC method, are presented here. A gain of time from 15 to 400 can be obtained by our method, with a mean difference in the dose calculation of about 1% in comparison with the analog MC method.
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Affiliation(s)
- H Elazhar
- Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France
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Arbor N, Higueret S, Elazhar H, Combe R, Meyer P, Dehaynin N, Taupin F, Husson D. Real-time detection of fast and thermal neutrons in radiotherapy with CMOS sensors. Phys Med Biol 2017; 62:1920-1934. [PMID: 28192285 DOI: 10.1088/1361-6560/aa5bc9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The peripheral dose distribution is a growing concern for the improvement of new external radiation modalities. Secondary particles, especially photo-neutrons produced by the accelerator, irradiate the patient more than tens of centimeters away from the tumor volume. However the out-of-field dose is still not estimated accurately by the treatment planning softwares. This study demonstrates the possibility of using a specially designed CMOS sensor for fast and thermal neutron monitoring in radiotherapy. The 14 microns-thick sensitive layer and the integrated electronic chain of the CMOS are particularly suitable for real-time measurements in γ/n mixed fields. An experimental field size dependency of the fast neutron production rate, supported by Monte Carlo simulations and CR-39 data, has been observed. This dependency points out the potential benefits of a real-time monitoring of fast and thermal neutron during beam intensity modulated radiation therapies.
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Affiliation(s)
- Nicolas Arbor
- Université de Strasbourg, IPHC, 23 rue du Loess 67037 Strasbourg, France. CNRS, UMR7178, 67037 Strasbourg, France
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Alikaniotis K, Borla O, Monti V, Vivaldo G, Zanini A, Giannini G. Radiotherapy dose enhancement using BNCT in conventional LINACs high-energy treatment: Simulation and experiment. Rep Pract Oncol Radiother 2016; 21:117-22. [PMID: 26933394 PMCID: PMC4747660 DOI: 10.1016/j.rpor.2015.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 03/19/2015] [Accepted: 07/21/2015] [Indexed: 10/23/2022] Open
Abstract
AIM To employ the thermal neutron background that affects the patient during a traditional high-energy radiotherapy treatment for BNCT (Boron Neutron Capture Therapy) in order to enhance radiotherapy effectiveness. BACKGROUND Conventional high-energy (15-25 MV) linear accelerators (LINACs) for radiotherapy produce fast secondary neutrons in the gantry with a mean energy of about 1 MeV due to (γ, n) reaction. This neutron flux, isotropically distributed, is considered as an unavoidable undesired dose during the treatment. Considering the moderating effect of human body, a thermal neutron fluence is localized in the tumour area: this neutron background could be employed for BNCT by previously administering (10)B-Phenyl-Alanine ((10)BPA) to the patient. MATERIALS AND METHODS Monte Carlo simulations (MCNP4B-GN code) were performed to estimate the total amount of neutrons outside and inside human body during a traditional X-ray radiotherapy treatment. Moreover, a simplified tissue equivalent anthropomorphic phantom was used together with bubble detectors for thermal and fast neutron to evaluate the moderation effect of human body. RESULTS Simulation and experimental results confirm the thermal neutron background during radiotherapy of 1.55E07 cm(-2) Gy(-1). The BNCT equivalent dose delivered at 4 cm depth in phantom is 1.5 mGy-eq/Gy, that is about 3 Gy-eq (4% of X-rays dose) for a 70 Gy IMRT treatment. CONCLUSIONS The thermal neutron component during a traditional high-energy radiotherapy treatment could produce a localized BNCT effect, with a localized therapeutic dose enhancement, corresponding to 4% or more of photon dose, following tumour characteristics. This BNCT additional dose could thus improve radiotherapy, acting as a localized radio-sensitizer.
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Affiliation(s)
- Katia Alikaniotis
- Department of Physics, University of Turin, Via Pietro Giuria 1, 10126 Torino, Italy
| | - Oscar Borla
- Polytechnic of Turin, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
| | - Valeria Monti
- Department of Physics, University of Turin, Via Pietro Giuria 1, 10126 Torino, Italy
| | | | - Alba Zanini
- INFN of Turin, Via Pietro Giuria 1, 10126 Torino, Italy
| | - Gianrossano Giannini
- Department of Physics, University of Trieste and INFN of Trieste, Via Valerio 2, 34127 Trieste, Italy
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Monte Carlo characterizations mapping of the (γ,n) and (n,γ) photonuclear reactions in the high energy X-ray radiation therapy. Rep Pract Oncol Radiother 2013; 19:30-6. [PMID: 24936317 DOI: 10.1016/j.rpor.2013.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 04/13/2013] [Accepted: 07/07/2013] [Indexed: 11/24/2022] Open
Abstract
AIM The aim of this work was to map the characteristics of (n,γ) and (γ,n) reactions in a high energy photon radiation therapy. BACKGROUND Photoneutrons produced in the high energy X-Ray radiation therapy may damage patients and staff. It is due to high RBE of the produced neutrons according to their energy and isotropic emission. Characterization of the photoneutrons can help us in appropriate shielding. MATERIALS AND METHODS This study focused on the photoneutron and capture gamma ray phenomena. Characteristics such as dose value, fluence and spectra of both the neutrons and the by produced prompt gamma ray were described. RESULTS AND DISCUSSION Neutron and prompt gamma spectra in different points showed the neutrons to be thermalized when increasing the distance from the linac. Energy of the neutrons changed from about 0.6 MeV at the isocentre to around 10(-08) MeV at the outer door position. Although the neutrons were found as fast neutrons, their spectra showed they were thermal neutrons at the outer door position. Additionally, it was seen that the energy of the gamma rays is higher than the scattered X-ray energy. The energy of gamma rays was seen to be up to 10 MeV while the linac photons had energy lower than 1 MeV. Neutron source strength obtained in this work was in good agreement with the published data, which may be a confirmation of our simulation accuracy. CONCLUSION The study showed that the Monte Carlo simulation can be applied in the radiotherapy and industrial radiation works as a useful and precise estimator. We also concluded that the dose from the prompt gamma ray at the outer door location is higher than the scattered radiation from the linac and should be considered in the shielding.
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Mesbahi A, Azarpeyvand AA, Shirazi A. Photoneutron production and backscattering in high density concretes used for radiation therapy shielding. ANN NUCL ENERGY 2011. [DOI: 10.1016/j.anucene.2011.08.023] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Naseri A, Mesbahi A. A review on photoneutrons characteristics in radiation therapy with high-energy photon beams. Rep Pract Oncol Radiother 2010; 15:138-44. [PMID: 24376940 DOI: 10.1016/j.rpor.2010.08.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Revised: 08/09/2010] [Accepted: 08/19/2010] [Indexed: 11/26/2022] Open
Abstract
In radiation therapy with high-energy photon beams (E > 10 MeV) neutrons are generated mainly in linacs head thorough (γ,n) interactions of photons with nuclei of high atomic number materials that constitute the linac head and the beam collimation system. These neutrons affect the shielding requirements in radiation therapy rooms and also increase the out-of-field radiation dose of patients undergoing radiation therapy with high-energy photon beams. In the current review, the authors describe the factors influencing the neutron production for different medical linacs based on the performed measurements and Monte Carlo studies in the literature.
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Affiliation(s)
- Alireza Naseri
- Radiation Therapy Department, Imam Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Asghar Mesbahi
- Radiation Therapy Department, Imam Hospital, Tabriz University of Medical Sciences, Tabriz, Iran ; Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran
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Zanini A, Fasolo F, Visca L, Durisi E, Perosino M, Annand JRM, Burn KW. Test of a bubble passive spectrometer for neutron dosimetry. Phys Med Biol 2005; 50:4287-97. [PMID: 16148394 DOI: 10.1088/0031-9155/50/18/004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A passive system for neutron spectrometry has been tested in view of neutron dose evaluation in mixed radiation fields. This system, based on bubble detectors (Bubble Technology Industries, Ontario, Canada), is suitable to evaluate the neutron energy distribution in the range 10 keV-20 MeV even in the presence of intense gamma radiation, as required in various fields: medical x-ray accelerators, nuclear reactors, cosmic ray exposures on commercial high-altitude flights and space missions. A new unfolding code BUNTO has been especially developed for this application. In the present work, the results of two experimental tests are summarized. In the first one, the device has been exposed to a standard AmBe neutron source (Joint Research Centre, Ispra, Varese, Italy). In the second one, measurements have been carried out at the MAX-Lab photonuclear facility in Sweden, with a bremsstrahlung photon beam impinging on thick targets of different materials and generating a giant dipole resonance neutron spectrum. Simulations of the experimental apparatus have been performed with MCNP4B (AmBe source) and with MCNP4B-GN (MAX-Lab). Results of the comparison between experimental and calculated spectra are shown and discussed. A good agreement between measurements and simulation data is obtained in both the experiments.
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Affiliation(s)
- A Zanini
- INFN Sez. Torino, V P Giuria 1, 10125 Torino, Italy.
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Zanini A, Durisi E, Fasolo F, Ongaro C, Visca L, Nastasi U, Burn KW, Scielzo G, Adler JO, Annand JRM, Rosner G. Monte Carlo simulation of the photoneutron field in linac radiotherapy treatments with different collimation systems. Phys Med Biol 2004; 49:571-82. [PMID: 15005166 DOI: 10.1088/0031-9155/49/4/008] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Bremsstrahlung photon beams produced by linac accelerators are currently the most commonly used method of radiotherapy for tumour treatments. When the photon energy exceeds 10 MeV the patient receives an undesired dose due to photoneutron production in the accelerator head. In the last few decades, new sophisticated techniques such as multileaf collimators have been used for a better definition of the target volume. In this case it is crucial to evaluate the photoneutron dose produced after giant dipole resonance (GDR) excitation of the high Z materials (mainly tungsten and lead) constituting the collimator leaves in view of the optimization of the radiotherapy treatment. A Monte Carlo approach has been used to calculate the photoneutron dose arising from the GDR reaction during radiotherapy with energetic photon beams. The simulation has been performed using the code MCNP4B-GN which is based on MCNP4B, but includes a new routine GAMMAN to model photoneutron production. Results for the facility at IRCC (Istituto per la Ricerca e la Cura del Cancro) Candiolo (Turin), which is based on 18 MV x-rays from a Varian Clinac 2300 C/D, are presented for a variety of different collimator configurations.
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Affiliation(s)
- A Zanini
- INFN Turin, Via P Giuria 1, 10125 Turin, Italy.
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Zanini A, Durisi E, Fasolo F, Visca L, Ongaro C, Nastasi U, Burn KW, Annand JRM. Neutron spectra in a tissue equivalent phantom during photon radiotherapy treatment by LINACS. RADIATION PROTECTION DOSIMETRY 2004; 110:157-160. [PMID: 15353639 DOI: 10.1093/rpd/nch205] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Bremsstrahlung photon beams produced by LINAC accelerators are currently the most used radiotherapy method for tumour treatments. When the photon energy exceeds the (gamma,n) reaction threshold energy, the patient receives an undesired dose due to photoneutron production both in the accelerator head and in the human body. In this paper, a method is presented for the assessment of the photoneutron spectra produced by Giant Dipole Resonance (GDR) during cancer radiotherapy with energetic photon beams. Experimental and numerical results have been obtained for the facility at Onkologik Klinik, Lund (Sweden), which is based on an ELEKTA 18 MV LINAC. Neutron spectra are evaluated both at the patient plane and inside an anthropomorphic phantom.
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Affiliation(s)
- A Zanini
- INFN, Via P. Giuria 1, 10125 Torino, Italy
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